1. Field of the Invention
The present invention relates generally to teaching aids and more specifically to a teaching aid for developing learner participation in mental computation of number combinations involving elements of basic arithmetic.
2. Description of the Prior Art
Various teaching aids and the like have heretofore been developed. See, for example, Finch, U.S. Pat. No. 275,475; Gillis, U.S. Pat. No. 416,593; Erwin, U.S. Pat. No. 711,486; Oldroyd, U.S. Pat. No. 894,043, Newman, U.S. Pat. No. 1,028,378; Robbins, U.S. Pat. No. 1,211,625; Warneke, U.S. Pat. No. 3,477,146; Bianchi, U.S. Pat. No. 3,491,193; Tarrant, U.S. Pat. No. 3,758,971; and Garruto, U.S. Pat. No. 3,969,832. None of the above patents disclose or suggest the present invention.